Hemophilia A wata cuta ce ta kwayoyin halitta da ke da karancin clotting factor VIII, furotin da ke taimakawa jini ya toshe. Mutanen da ke da Hemophilia A suna fuskantar haɗarin zubar da jini mai yawa da kururuwa, musamman bayan rauni ko tiyata. Mummunan yanayin na iya bambanta, tare da wasu mutane suna fuskantar ƙananan alamu yayin da wasu kuma suna fuskantar yanayin zubar jini mai tsanani wanda zai iya zama haɗari. Hemophilia A wani yanayi ne da aka gada wanda ake yadawa daga iyaye zuwa yaro ta hanyar maye gurbi a cikin kwayar halittar F8 dake kan X chromosome. Da farko yana shafar maza, saboda suna da X chromosome guda ɗaya kawai, yayin da mata ke da X chromosomes guda biyu kuma galibi su ne masu ɗaukar kwayar halitta.